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A versatile sensing platform employing inorganic MoS2nanoflowers and organic poly(3,4-ethylene dioxythiophene): poly (styrene sulfonate) (PEDOT:PSS) has been investigated to develop the resistive and capacitive force-sensitive devices. The microstructure of the sensing layer heightens the sensitivity and response time of the dual-mode pressure sensors by augmenting electron pathways and inner stress in response to mechanical stimuli. Consequently, the capacitive and resistive sensors exhibit sensitivities of 0.37 and 0.12 kPa−1, respectively, while demonstrating a remarkable response time of approximately 100 ms. Furthermore, it is noteworthy that the PEDOT:PSS layer exhibits excellent adhesion to polydimethylsiloxane (PDMS) substrates, which contributes to the development of highly robust force sensitive sensors capable of enduring more than 10000 loading/unloading cycles. The combination of MoS2/PEDOT:PSS layers in these dual-mode sensors has shown promising results in detecting human joint movements and subtle physiological signals. Notably, the sensors have achieved a remarkable precision rate of 98% in identifying target objects. These outcomes underscore the significant potential of these sensors for integration into applications such as electronic skin and human-machine interaction.

Dissimilar metal welding, such as welding stainless steel to the titanium alloy, provides a new method to achieve low-cost applications and keep high mechanical properties of the Ti alloys. However, the welding strength is limited by the brittle intermetallic compounds generated in the welding process. In this paper, a melt inert-gas welding (MIG) method that assisted with a CuSi3 filler is used to realize the high-strength welding of TC4 titanium alloy and 304 ss stainless steel. The influences of heat input on the microstructure composition, reaction layer thickness, mechanical properties, fracture behavior, and microhardness distribution in the interface are systematically studied to reveal the interfacial interfusion mechanism during the welding process. In addition, it was suggested that the brittle intermetallic compounds (IMCs) such as FexTi and CuxTiyin the interface are identified under the optimal welding parameters, and the maximum tensile strength of the welded joint was beyond 266 MPa. The dissimilar metal welding of TC4 and 304 ss presented in this paper has good prospects for application aerospace, nuclear industries, and offshore foundations.

In order to suppress the axial vibration stripes machining defects (AVSMD) and achieve the engineering goal of multi-demand high quality processing with grain refinement during side milling of GH4169 superalloy, the defect formation mechanism in conventional side milling (CSM) and the defect suppression mechanism in ultrasonic vibration-assisted side milling (UVASM) have been investigated respectively. The impact of ultrasonic high-frequency energy field on subsurface grain refinement was also investigated intensively. The results show that the axial vibration stripes width proportion factor (AVSWPF) in UVASM was quantitatively and numerically smaller than the AVSWPF in CSM. Furthermore, the mechanism of machining defect suppression in UVASM was fully analyzed with three aspects. Compared to CSM, the frequency fraction of small diameter grains (3.51 μm) and the average grain diameter in UVASM were respectively reduced by 26.2 % and 10.7 % due to the continuous intervention of ultrasonic high-frequency energy impact. The finer grains and higher residual compressive stress can be achieved in UVASM, thus improving the wear resistance, strength, and fatigue life of the material to some extent. The results show that defect suppression and grain refinement can be achieved simultaneously in UVASM processing, which has great research value for the formability processing of series superalloys.

Torrefaction is a process of mild pyrolysis at 200–300 °C under nitrogen atmosphere and has been considered to be an effective way to improve the properties of biomass. In this study, lignin was subjected to torrefaction at 200 °C, 230 °C, 260 °C, and 290 °C. Thermogravimetric analysis of lignin samples was performed at a temperature ramp of 25 to 550 °C with the heating rates of 10, 20, 30, or 40 °C min−1. A distributed activation energy model was used to analyze the pyrolysis kinetics of lignin. Then, the lignin samples were subjected to pyrolysis at 600 °C for 10 s. The results showed that torrefaction had a significant effect on the physicochemical properties and pyrolysis characteristics of lignin. Among the torrefied samples, the sample treated at 290 °C exhibited the lowest mass yield (86.07%), lowest energy yield (93.25%), highest content of carbon (63.76%), highest higher heating value (25.18 MJ kg−1), and lowest content of oxygen (30.25%). The activation energy of torrefied lignin samples slightly changed in comparison with those of the raw samples. Torrefaction has a significant effect on pyrolysis products. The peak area % of S-type (41.4%) and P-type (5.4%) phenols in the bio-oil obtained by pyrolysis of LN-200 was the highest.

In this study, soybean straw pellets (SSP) and pine wood pellets (PWP) were used as materials for torrefaction at 200–350 °C. Impacts of torrefaction temperature on the physicochemical properties, hydrophobicity, and mechanical properties of the pellets were investigated. Results showed that some oxygen-containing functional groups in the biomass pellets disappeared during torrefaction, and the oxygen content significantly decreased. The hydrophobic behavior of biomass is highly affected by their chemical composition. A significant decrease in hemicellulose content was observed in torrefied pellets. Consequently, the equilibrium moisture content of torrefied pellets decreased significantly; and the torrefied PWP remained intact even after immersion of more than 2 h in water. As the torrefaction temperature increased, the cellulose and lignin started to decompose and formed more micropores. Meanwhile, the torrefied pellets became less dense, which lowered the mechanical properties of the pellets. Optimal temperature for the preparation of high-quality torrefied SSP and torrefied PWP was found to be 250 °C and 300 °C, respectively, since higher temperatures cause excessive loss of volatiles and degradation of mechanical properties without significantly enhancing the high heating value of torrefied pellets.

The study to obtain a sound joint between aluminum and steel is rather challenging due to the large mismatch in thermal properties and the formation of brittle IMCs, especially for press-hardened steel attributing to its martensite microstructure. In this present study, dissimilar joining of 5052 aluminum and press-hardened steel was comprehensively explored by employing laser offset welding without any fillers and interlayers. The influence of laser offset on welding appearance and mechanical properties was evaluated. The microstructure analysis, bonding mechanism, and fracture behavior were identified and characterized by means of optical microscope (OM), scanning electron microscope (SEM), energy-dispersive X-ray spectrometer (EDS), and X-ray diffraction (XRD). The satisfactory welding appearance and mechanical property of 129.6MPa was obtained at the laser offset of 0.2mm. The interface microstructure was composed of continuous Fe2Al5, acicular Fe4Al13and islands IMCs. In addition, micro cracks could be initiated spontaneously in Fe2Al5layer due to the residual stress, whereas a consecutive crack seems be induced by a micro pore defect. No matter what the fracture mode was during tensile test, the fracture surface was localized at the welded interface.

Water has been labeled as a devil in fabrication and stability of perovskite solar cells. The inherent cognition impels researchers to prepare perovskite films in water-controlled conditions. Herein, water is used as a green solvent to prepare CsPbBr3films through a two-step spin-coating method. Due to the high solubility of CsBr but low solubility of PbBr2in water, it provides a possibility to deposit CsBr onto PbBr2from water solution without destroying the film. Here, high-quality CsPbBr3films are fabricated by spin-coating concentrated CsBr/H2O solution onto the PbBr2film followed by annealing. As a result, the solar cells basing on a configuration of FTO/TiO2/CsPbBr3/Carbon exhibit a power conversion efficiency of 6.12%. This work provides a simple and easy way to prepare high-quality CsPbBr3films for efficient solar cells. It makes a solid step toward reducing the solvent toxicity in the fabrication process of perovskite solar cells. It also breaks the forbidden zone for fabricating perovskite films from water and updates the inherent understanding of water in the research study of perovskite solar cells.

High quality perovskite films with large columnar grains are greatly desired for efficient perovskite solar cells. Here, low volatility N-methyl-2-pyrrolidone (NMP) was added in MAI/IPA solution in a two-step spin-coating method, which promoted the conversion of lead iodide to perovskite. The perovskite films were annealed by a closed-steam annealing method to prolong the recrystallization process of perovskite films assisted by the residual NMP. It leaded to high quality CH3NH3PbI3perovskite films with large columnar grains due to its enhancement of the Oswald ripening. The large grain perovskite film leaded to efficient carrier transformation and injection, and low recombination. The photovoltaic performance of the perovskite solar cells was improved significantly.

Recently, perovskite solar cells have attracted great attention because of their outstanding photovoltaic performance and ease of fabrication. High-quality perovskite films hold a key in getting highly efficient perovskite solar cells. Solution-processed fabrication technique is the most widely adopted for preparing perovskite films because of its low cost. In the solution-proceed perovskite films, solvents not only play the role of dissolving the solute but also participate in the crystallization of perovskite. In the one-step method, solvents play key roles in controlling morphology, widening process window, and achieving room-temperature crystallization of perovskite films. In addition, the solvents play important roles in controlling the nuclei/growth, suppressing volume expansion during the two-step method. Especially, the solvent can induce grain coarsening during the annealing process. A deep understanding of the multiplicity of roles during the formation of perovskite films will help understand the formation mechanism of perovskite films. Here, a systematic review on the progress in fabrication of high-quality perovskite films by making use of solvent to control the crystallization is presented. Meanwhile, we elucidate the key roles of solvent in the fabrication of high-quality perovskite films.

Perovskite films are usually fabricated by a solution-processed method due to its low cost and ease of fabrication. The organic solvent plays multiple roles in the growth of perovskites. Here, we investigate the growth of methylammonium lead iodide perovskite and its intermediate phase from microdroplets containing various solvents. The perovskite intermediate phase inclines to grow in the direction of its (020) plane from polar aprotic solvents at low temperature. At high temperature, the growth of perovskites depends on the structure of solvent molecules. The intermediate phase still grows from the solvents with a short chain structure. It tends to form smooth films containing radial domains with dimensions in tens of microns, which consist of nanocrystals due to annealing effects. However, perovskite grains grow directly from the solvents with a ring structure. It tends to form smooth thin films by joining the large hexagonal perovskite crystals together. It provides a guidance to prepare high quality perovskite films for high performance optoelectronic devices.

High-quality perovskite films can be fabricated from Lewis acid–base adducts through molecule exchange. Substantial work is needed to fully understand the formation mechanism of the perovskite films, which helps to further improve their quality. Here, we study the formation of CH3NH3PbI3perovskite films by introducing some dimethylacetamide into the PbI2/N,N-dimethylformamide solution. We reveal that there are three key processes during the formation of perovskite films through the Lewis acid–base adduct approach: molecule intercalation of solvent into the PbI2lattice, molecule exchange between the solvent and CH3NH3I, and dissolution–recrystallization of the perovskite grains during annealing. The Lewis base solvents play multiple functions in the above processes. The properties of the solvent, including Lewis basicity and boiling point, play key roles in forming smooth perovskite films with large grains. We also provide some rules for choosing Lewis base additives to prepare high-quality perovskite films through the Lewis adduct approach.

Perovskite solar cells have a puzzling phenomenon of current hysteresis. Here, we modulate the hysteresis by applying a poling voltage. Charge accumulations are detected in the perovskite solar cells. Two interacting capacitors are identified through dynamic voltage measurement. We elucidate that the current hysteresis originates mainly from the polarization and depolarization of electric dipoles of CH3NH3+under an external electric field due to the intrinsic ferroelectric properties of perovskite. The polarization leads to charge accumulation at the surface of perovskite, which establishes a polarization-induced electric field. The polarization-induced electric field affects the charge transport inside the solar cells, resulting in the current hysteresis. The polarization of electric dipoles can be modified by the poling and sweeping voltage, which makes the hysteresis exhibit a history-dependent effect.

The aluminum-steel hybrid assemblies would simultaneously reach the engineering aim to reduce weight and improve fuel efficiency. However, it is of great challenge to join aluminum to steel due to the great difference in thermal properties and the formation of IMC. In this work, a better joint between aluminum and Al-Si coated boron steel was successfully achieved using laser/DP-MIG hybrid welding-brazing. The examinations of welding appearance, macrostructure, interface microstructure, and tensile tests were carried out. The laser/DP-MIG hybrid welding-brazing could simultaneously strengthen metallurgic bonding and wettability compared to conventional MIG joint. The plasma characteristics of laser/DP-MIG hybrid source contributes to suppress the formation and growth of IMC. Three phases and its formation mechanism were demonstrated in detail: τ5-Fe2Al8Si, θ-Fe(Al,Si)3, and η-Fe2(Al,Si)5. The average joint strength of laser/DP-MIG was 271.8 N/mm whereas that of conventional MIG was 138.4 N/mm. The substantial adhesion area at the brazing interface and the brittle IMC is the two main factors in determining the tensile strength.

Dion-Jacobson (DJ) quasi-2D perovskite solar cells (PSCs) have received increasing attention due to their greater potentials in realizing efficient and stable quasi-2D PSCs relative to their Ruddlesden–Popper counterpart. The substitution of methylammonium (MA+) with formamidinium is expected to be able to further increase the stability and power conversion efficiency (PCE) of DJ quasi-2D PSCs. Herein, we report a multifunctional additive strategy for preparing high-quality MA-free DJ quasi-2D perovskite films, where 1,1′-carbonyldi(1,2,4-triazole) (CDTA) molecules are incorporated into the perovskite precursor solution. CDTA modification can control phase distribution, enlarge grain size, modulate crystallinity and crystal orientation, and passivate defects. After CDTA modification, more favorable gradient phase distribution and accordingly gradient band alignment are formed, which is conducive to carrier transport and extraction. The improved crystal orientation can facilitate carrier transport and collection. The enlarged grain size and effective defect passivation contribute to reduced defect density. As a result, the CDTA-modified device delivers a PCE of 16.07%, which is one of the highest PCEs ever reported for MA-free DJ quasi-2D PSCs. The unencapsulated device with CDTA maintains 92% of its initial PCE after aging under one sun illumination for 360 h and 86% after aging at 60 °C for 360 h.